Introduction: GRBL Losing Steps ? 5 Simple Tips to Fix It Fast !

Is Your CNC losing steps? lines dont connect when they should and do contact when they shouldn't ?

this instructable might help you get rid of that problem !

Step 1: Lower the Voltage

Although the GRBL board is marked 12-36V, stepper driver might not like the full 36V for example the A4988 works up to 35V datasheat it all depends on which stepper driver are You using. Look for its datasheet to check the voltage suitable for it.

If Your using similar power supply to the one i do (my power suppl) use the voltage adjustment potentiometer

I suggest setting just under 30V.

Step 2: Use Microstepping

Microstepping reduces the amplitude of the torque variations between steps, which reduces the excitation of the pendulum resonance, and thus the likelihood that the error angle will get large enough to lose steps.

Very good article on the topic can be found here

To set microstepping just put a jumper(s) in desired position(s) Half step worked for Me just fine. Remember to increase number of steps per mm or in in grbl setup.

$100=XXX.XXX (x, step/mm)

$101=XXX.XXX (y, step/mm)

$102=XXX.XXX (z, step/mm)

If You use half step You need to double the steps per mm/in

Step 3: Reduce Speed of the Stepper Motors

If You are using leadscrews. Try to set grbl config so that the stepper spins no more than approximately 350rpm.When the stepper is rotating slower the time betwin steps increases and significantly lowers motor resonance

$110=XXX.000 (x max rate, mm/min) $111=XXX.000 (y max rate, mm/min)

$112=XXX.000 (z max rate, mm/min)

to calculate RPMs you need to know how many mm/in is your stepper moving per one revolution

acceleration should be about 10% lower than the max speed

$120=(XXX-10%).000 (x accel, mm/sec^2) $121=(XXX-10%).000 (y accel, mm/sec^2)

$122=(XXX-10%).000 (z accel, mm/sec^2)

My motors work best at 300 rpms although they can go much faster

Step 4: Use Brakes on the Motor

Set the step idle delay to 255. This will hold the motor in place when it is not turning. Otherwise the vibrations may cause a little bit of drift

$1=255 (step idle delay, msec)

Step 5: Use Cooling

Stepper drivers have over temperature shutdown protection so if they are off for just a split second You're losing a lot of steps

Old pc cpu fan blowing directly at the steper drivers radiators will do the job just fine. Remember thy work on 12V so if you're using more you have to step it down for example by using adjustable step down power Supply module

Step 6: THX

Thac all my tips and tricks. They have solve my problem maybe they will help You too

If im wrong in anything or i did some mistake please correct Me

Thx for reading hope the info becomes useful :)

Comments

author
pfred2 (author)2016-12-21

Your problem lies in GRBL itself. GRBL does not have a trajectory planner, so it does not compensate for inertia. That means you have to cripple your machine's performance for it to work right. Or put another way, you have to run slow enough that inertia is not a factor. I have 90 inch per minute rapids on my machine, which means my lead screws are turning 900 RPM at that speed. If my machine could only run 350 RPM I'd take it out back, and shoot it!

author
PiotrS (author)pfred22016-12-21

for my use it is even to fast :) + grbl is 7$

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Bio: Jungest out of 5, 1 brother 3 sisters i have lerned something from each one of them :)
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